In recent years, a controlled device including a wireless authentication function of unlocking if it is determined that the reception strength of a radio wave received from a wireless key (a wireless communication unit) is equal to or greater than a predetermined value and that authentication with the wireless key results in success based on a signal transmitted and received using the wireless communications; and locking if it is determined that the reception strength of a radio wave received from the wireless key is less than the predetermined value or that authentication with the wireless key results in failure has been proposed (for example, patent document 1). As an example of a controlled device put to practical use, an automobile for locking or unlocking a door key by conducting wireless authentication with a wireless key, a mobile telephone for rejecting or permitting acceptance with an operation key by conducting wireless authentication with a wireless key, or the like can be named.    Patent document 1: JP-A-2004-143806